This invention concerns a method of detecting peroxide-based explosives and a kit for use in this method.
Improvised explosive devices based on peroxide containing materials have increasingly been used in recent years by various terrorist organizations, especially in Israel, as well as in the UK and the USA. The main reason is that such peroxide-based explosives can be easily xe2x80x9chome-madexe2x80x9d using inexpensive, readily available starting materials which can be purchased in most hardware and paint stores, even in bulk quantities. One class of such peroxide-based explosives can be easily produced by reacting various carbonyl compounds (e.g. ketones, aldehydes and their derivatives) with hydrogen peroxide under acid catalysis. For example, when a mixture of acetone, hydrogen peroxide and small amounts of a mineral acid, e.g. sulfuric acid, is left for several hours at room temperature, white crystals of triacetone triperoxide (hereinafter xe2x80x9cTATPxe2x80x9d) and diacetone diperoxide (hereinafer xe2x80x9cDADPxe2x80x9d) are formed by the following reaction: 
These crystals are collected and can be stashed with water or with 10% sodium carbonate solution. TATP and DADP are powerful initiators by themselves and can be used as the main filler in home-made detonators. They are quite unstable explosives and may explode under rough handling, scratching with metals or by sparks and open flame, even when they contain up to 25% water or even when immersed in water. The explosive intensity of TATP is approximately ⅝ that of TNT. This material is quite volatile, unless used shortly after its manufacture, should be stored in a cool, dark dry place. It has been reported that at room temperature TATP loses ⅔ of its weight within 14 days and at 50xc2x0 C. it evaporates completely within 40 days.
Another commonly used peroxide based explosive is hexamethylenetriperoxidediamine (hereinafter xe2x80x9cHMTDxe2x80x9d). It can be conveniently prepared by treating hexamethylenetetramine with hydrogen peroxide in the presence of a weak acid, such as citric acid, in order to neutralize the liberated ammonia. The reaction can be represented as follows: 
HMTD is almost insoluble in water and in common organic solvents at room temperature. It is too active and too unstable to be of commercial use as an explosive.
Although many peroxide containing materials of the above-described type are known for more than 70 years, no satisfactory method for their detection has been suggested to date. The detection of peroxide-based explosives is particularly difficult because all these materials do not contain nitro groups or any other nitrogen oxide functional groups. Since most of the currently available explosive detectors are based on the detection of nitro groups, they cannot be employed for detection of peroxide-based materials. Consequently, and in view of the increased use of such peroxide-based explosives by terrorists, especially in the Middle East as well as in other parts of the world, there exists an urgent need for highly sensitive method, and devices for the early detection of peroxide-based explosives and improvised explosive devices employing them.
It is thus the object of the present invention to provide a reliable method for the fast and easy detection of peroxide-based explosives.
It is a further object of the invention to provide a portable kit for the simple yet reliable and selective detection and identification of peroxide based explosives.
The above object was achieved by the present invention which provides a method of detecting a peroxide-based explosive in a sample suspected of consisting of or comprising such explosive, which method comprises dissolving said sample in a suitable organic solvent, contacting the solution with an aqueous solution of a strong acid capable of decomposing said explosive to release hydrogen peroxide, and contacting the resulting mixture with a peroxidase enzyme, a buffer to adjust the pH to such permitting action of the peroxidase enzyme and a substrate capable of being oxidized by the oxidant under the catalysis of the peroxidase enzyme to produce a pronounced change in a measurable physical parameter of the substrate.
The invention also provides, in a second aspect thereof, a kit for use in a method of the invention, comprising packaged organic solvent, packaged aqueous solution of a strong acid, packaged buffer, packaged peroxidase enzyme and packaged substrate.